Currently, after a user equipment (UE) accesses an evolved packet core (EPC) network by using, for example, a 3rd Generation Partnership Project (3GPP) network, and establishes a packet data network (PDN) connection and obtains an Internet Protocol (IP) address (first IP address) through a packet data network gateway (PDN-GW) (first PDN-GW), if the UE accesses the EPC by using, for example, a trusted wireless local area network access network (TWAN), a home subscriber server or an authentication, authorization and accounting server (HSS/AAA) allocates a default access point name (APN) to the TWAN according to subscription information of the UE, so that when a PDN connection is established, the TWAN selects a PDN-GW (second PDN-GW) to establish the PDN connection, where the second PDN-GW uses the default APN to allocate an IP address (second IP address) to the UE.
However, in a case where the TWAN uses the default APN to establish the PDN connection, it cannot be ensured that the first PDN-GW used for establishing the PDN connection in the 3GPP network is the same as the second PDN-GW used for establishing the PDN connection in the TWAN, and even in a case where the first PDN-GW and the second PDN-GW are the same, it cannot be ensured that the second IP address and the first IP address are the same. Therefore, service continuity cannot be ensured.